An example of a lance departure prevention device is described in Japanese Kokai Patent Application No. 2007-122569. According to the lane departure control described in Japanese Kokai Patent Application No. 2007-122569, when it is judged that the vehicle is going to depart from the travel lane, a departure prevention output (yaw moment) is applied to the vehicle. By applying the yaw moment, departure of the vehicle from the travel lane is prevented.